title: Studies of transalkylation of phosphotriesters in DNA: reaction conditions and requirements on nucleophiles for determination of DNA adducts.
abstract: Reactive compounds form adducts at several sites in DNA. One of these sites, the phosphate groups, forms phosphotriesters (PTE) which are both chemically stable and little repaired. A measurement of PTE in DNA could therefore be advantageous for the determination of doses in vivo of mutagens/cancer initiators. In this paper, the possibilities of utilizing the weakly alkylating properties of PTE for the transfer of adducts to strong nucleophiles have been investigated. Model compounds, thymidine 3'-[thymidine 5'-(methyl phosphate)], TpMeT, and thymidine 3'-[thymidine 5'-(2-hydroxyethyl phosphate)], TpHOEtT, were incubated with thiosulfate, a relatively strong nucleophile and the formation of dealkylated model PTE, thymidine 3'-(thymidine 5'-phosphate), TpT, was followed by HPLC. Transalkylation to thiosulfate or aniline of methyl PTE in DNA alkylated by [3H]N-methyl-N-nitrosourea was demonstrated. The methyl groups transferred, forming methyl thiosulfate and N-methylaniline, respectively, were determined by HPLC. These experiments demonstrate that it is possible to transfer alkyls from DNA phosphate to nucleophiles. Kinetic aspects of the transalkylation and requirement on nucleophiles for a practically useful method for determination of DNA adducts are discussed. Constants of reaction rates are presented.
authors.affiliation: Department of Genetic and Cellular Toxicology, Stockholm University, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Haglund
authors.forename: L
authors.initials: L
authors.lastname: Ehrenberg
authors.forename: M
authors.initials: M
authors.lastname: Törnqvist
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry*; D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D004247:DNA / Q000737:chemistry*; D018736:DNA Adducts / Q000737:chemistry*; D019175:DNA Methylation; D003640:Dealkylation; D003848:Deoxyguanine Nucleotides / Q000737:chemistry*; D008770:Methylnitrosourea / Q000737:chemistry; D013885:Thiosulfates / Q000737:chemistry*
chemical_list: D000814:Aniline Compounds; D018736:DNA Adducts; D003848:Deoxyguanine Nucleotides; D013885:Thiosulfates; D008770:Methylnitrosourea; D004247:DNA; C023650:aniline